People with environmental sensitivities, allergies and asthma are often taught to shun basements as dark, dank places laden with triggers such as mold and chemical fumes. And that stereotype can hold true. But the basement also presents much needed extra space. So let’s show you how to make your downstairs a safe, comfortable and breathable area.

Damp Downstairs

In school, we learn that hot air rises, and cold air falls. This means that in warmer weather, hot moist air leaks into your house and cools as it falls into the basement. As the hot air cools, the relative humidity is increasing as temperature drops, causing the damp feeling in the basement.

In fact, the air can reach the dew point – the temperature at which water falls out of it. When you add furnishings such as carpets and old upholstered furniture, which can absorb and hold the water vapor, this creates a musty, and potentially moldy basement.

As air moves through cracks in the basement walls, windows and elsewhere, it also brings with it dust, pollens and molds found outside. These end up in the basement as well. Add a few kids, pets and some glues and paints from hobbies and the workshop, and you’ve got the ingredients for an unhealthy space.

What To Do: Outside

To allergen-proof inside, start by minimizing what gets in. Grading is a major component of keeping your basement dry and refers to the slope of the land around the house. You want a “positive” slope or grade – which means the water runs away from the house.

With a “negative” slope, water pools and seeps into the ground, adding hydrostatic pressure to the foundation walls. Excessive water pressure will ultimately lead a wall system to fail and allow water to enter the basement. I recommend that you walk around your house during a heavy rain to assess how the water is moving around the building.

• Grading work does not have to be dramatic, but it must have a positive slope away from the building on all sides. How you can do this:
– Using a shovel and a wheelbarrow, create simple slopes in the areas of concern.
– Specifically, build up the soil closest to the house (keep it off siding, though), and dig down the soil that’s farther away from the building. Your slope must lose incline as you move away from the foundation. You can add grass seed to control erosion.

• The downspouts on your home are also extremely important as they release a large volume of water near the base of your home. It is imperative that downspouts direct water far away from the foundation. They should extend four to six feet from the building.

• Also consider the window wells. They keep snow off windows and ledges and reduce the risk of high water against a window, the weakest point in the basement walls. Wells should be at least six inches deeper than the bottom of the windowsill. The Canada Mortgage and Housing Corp. recommends that you then dig down a further six to eight inches and fill with gravel to aid in drainage. (I often take the gravel even deeper.)

• Waterproofing: The only way to ensure your basement is completely dry, however, is to dig out the foundation from the outside, and add a waterproofing barrier of some kind. That entails hiring a waterproofing company and can be expensive. Be sure to check references if dealing with a larger job, and call utility companies before they dig.